Method for plurality of processing time or plurality of transmission time intervals in wireless communication system, and apparatus therefor

ABSTRACT

A method by which a terminal supports a carrier aggregation and a short processing time in a wireless communication system, according to one embodiment of the present disclosure, comprises the steps of: reporting, to a base station, whether a terminal can support a short processing time when the carrier aggregation is configured; determining the processing time to be used by the terminal when a cross carrier aggregation is configured in the terminal; and performing an uplink transmission operation according to the determined processing time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/KR2017/010392, filed on Sep. 21, 2017, which claims the benefit ofU.S. Provisional Application No. 62/535,948, filed on Jul. 23, 2017,U.S. Provisional Application No. 62/491,382, filed on Apr. 28, 2017,U.S. Provisional Application No. 62/432,690, filed on Dec. 11, 2016,U.S. Provisional Application No. 62/423,157, filed on Nov. 16, 2016,U.S. Provisional Application No. 62/401,960, filed on Sep. 30, 2016, andU.S. Provisional Application No. 62/401,850, filed on Sep. 29, 2016. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a method and apparatus for a plurality ofprocessing times or a plurality of transmission time intervals (TTIs).

BACKGROUND ART

The latency of packet data is one of important performance metrics. Toreduce the latency of packet data and provide faster Internet access toan ender user is one of challenging issues in designing thenext-generation mobile communication system called new radio accesstechnology (RAT) as well as long term evolution (LTE).

The present disclosure is intended to deal with uplink transmission suchas transmission of a hybrid automatic repeat request (HARD) feedback oruplink data in a wireless communication system supporting latencyreduction.

DISCLOSURE Technical Problem

The present disclosure relates to capability reporting of a userequipment (UE) having a plurality of processing times in carrieraggregation (CA), a UE operation based on CA and the plurality ofprocessing times, and a UE operation for supporting a short transmissiontime interval (TTI) or a plurality of TTIs in CA.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

According to an embodiment of the present disclosure, a method ofsupporting carrier aggregation and a shortened processing time in awireless communication system, performed by a user equipment (UE) mayinclude if carrier aggregation is configured for the UE, reporting to abase station (BS) whether the UE supports the shortened processing time,if cross carrier aggregation is configured for the UE, determining aprocessing time to be used for the UE, and performing an uplinktransmission operation according to the determined processing time.

Alternatively or additionally, the report of whether the shortenedprocessing time is supported may include information indicating whetherthe shortened processing time is supported for each number of carriersused for the carrier aggregation or for each group of numbers ofcarriers used for the carrier aggregation.

Alternatively or additionally, the report of whether the shortenedprocessing time is supported may be provided on a band basis or on aband combination basis.

Alternatively or additionally, the report of whether the shortenedprocessing time is supported may include information about a supportedprocessing time for each band or band combination.

Alternatively or additionally, the report of whether the shortenedprocessing time is supported may include information about a maximumnumber of carriers for which the shortened processing time is supportedin each band or band combination.

Alternatively or additionally, if more than the maximum number ofcarriers are configured or activated for the UE, a processing time foruse in the UE may be determined to be a predetermined processing time.

Alternatively or additionally, when two serving cells for cross-carrierscheduling are configured for the UE, if the two serving cells havedifferent processing times, the uplink transmission operation may beperformed according to a longer processing time of the processing timesof the two serving cells.

Alternatively or additionally, when two serving cells for cross-carrierscheduling are configured for the UE, the two serving cells may have thesame processing time.

Alternatively or additionally, the uplink transmission operation mayinclude an operation of transmitting a hybrid automatic repeat request(HARQ) feedback for downlink data reception or an uplink datatransmission operation according to reception of an uplink grant.

Alternatively or additionally, the UE may be configured to support twoor more processing times.

Alternatively or additionally, if the timings of HARQ feedbacks fordownlink data receptions having different processing times overlap witheach other, each DL data may be limited to one codeword.

Alternatively or additionally, when the timings of HARQ feedbacks fordownlink data receptions having different processing times overlap witheach other, if downlink data scheduled by specific downlink controlinformation is two codewords, HARQ feedbacks for the two codewords maybe bundled.

Alternatively or additionally, if cells aggregated for the carrieraggregation support a downlink short transmission time interval (TTI), adownlink short TTI may be configured for each cell, each cell group, oreach physical uplink control channel (PUCCH) cell group.

Alternatively or additionally, if cells aggregated for the carrieraggregation support an uplink short TTI, an uplink short TTI may beconfigured for each cell, each cell group, or each physical uplinkcontrol channel (PUCCH) cell group.

According to another embodiment of the present disclosure, a UE forsupporting carrier aggregation and a shortened processing time in awireless communication system may include a receiver and a transmitter,and a processor configured to control the receiver and the transmitter.The processor may be configured, if carrier aggregation is configuredfor the UE, to report to a base station (BS) whether the UE supports theshortened processing time, if cross carrier aggregation is configuredfor the UE, to determine a processing time to be used for the UE, and toperform an uplink transmission operation according to the determinedprocessing time.

The aforementioned solutions are just a part of embodiments of thepresent disclosure. Various embodiments to which technicalcharacteristics of the present disclosure are reflected can be drawn andunderstood based on detail explanation on the present disclosure to bedescribed in the following by those skilled in the correspondingtechnical field.

Advantageous Effects

According to the embodiments of the present disclosure, uplinktransmission may be performed efficiently.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 is a diagram for an example of a radio frame structure used inwireless communication system;

FIG. 2 is a diagram for an example of a downlink (DL)/uplink (UL) slotstructure in a wireless communication system;

FIG. 3 is a diagram for an example of a downlink (DL) subframe structureused in 3GPP LTE/LTE-A system;

FIG. 4 is a diagram for an example of an uplink (UL) subframe structureused in 3GPP LTE/LTE-A system;

FIG. 5 illustrates an operation of a user equipment (UE) according to anembodiment of the present disclosure; and

FIG. 6 is a block diagram for a device configured to implementembodiment(s) of the present disclosure.

MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. The accompanying drawings illustrate exemplaryembodiments of the present disclosure and provide a more detaileddescription of the present disclosure. However, the scope of the presentdisclosure should not be limited thereto.

In some cases, to prevent the concept of the present disclosure frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

In the present disclosure, a user equipment (UE) is fixed or mobile. TheUE is a device that transmits and receives user data and/or controlinformation by communicating with a base station (BS). The term ‘UE’ maybe replaced with ‘terminal equipment’, ‘Mobile Station (MS)’, ‘MobileTerminal (MT)’, ‘User Terminal (UT)’, ‘Subscriber Station (SS)’,‘wireless device’, ‘Personal Digital Assistant (PDA)’, ‘wireless modem’,‘handheld device’, etc. A BS is typically a fixed station thatcommunicates with a UE and/or another BS. The BS exchanges data andcontrol information with a UE and another BS. The term ‘BS’ may bereplaced with ‘Advanced Base Station (ABS)’, ‘Node B’, ‘evolved-Node B(eNB)’, ‘Base Transceiver System (BTS)’, ‘Access Point (AP)’,‘Processing Server (PS)’, etc. In the following description, BS iscommonly called eNB.

In the present disclosure, a node refers to a fixed point capable oftransmitting/receiving a radio signal to/from a UE by communication withthe UE. Various eNBs can be used as nodes. For example, a node can be aBS, NB, eNB, pico-cell eNB (PeNB), home eNB (HeNB), relay, repeater,etc. Furthermore, a node may not be an eNB. For example, a node can be aradio remote head (RRH) or a radio remote unit (RRU). The RRH and RRUhave power levels lower than that of the eNB. Since the RRH or RRU(referred to as RRH/RRU hereinafter) is connected to an eNB through adedicated line such as an optical cable in general, cooperativecommunication according to RRH/RRU and eNB can be smoothly performedcompared to cooperative communication according to eNBs connectedthrough a wireless link. At least one antenna is installed per node. Anantenna may refer to an antenna port, a virtual antenna or an antennagroup. A node may also be called a point. Unlink a conventionalcentralized antenna system (CAS) (i.e. single node system) in whichantennas are concentrated in an eNB and controlled an eNB controller,plural nodes are spaced apart at a predetermined distance or longer in amulti-node system. The plural nodes can be managed by one or more eNBsor eNB controllers that control operations of the nodes or schedule datato be transmitted/received through the nodes. Each node may be connectedto an eNB or eNB controller managing the corresponding node via a cableor a dedicated line. In the multi-node system, the same cell identity(ID) or different cell IDs may be used for signal transmission/receptionthrough plural nodes. When plural nodes have the same cell ID, each ofthe plural nodes operates as an antenna group of a cell. If nodes havedifferent cell IDs in the multi-node system, the multi-node system canbe regarded as a multi-cell (e.g. macro-cell/femto-cell/pico-cell)system. When multiple cells respectively configured by plural nodes areoverlaid according to coverage, a network configured by multiple cellsis called a multi-tier network. The cell ID of the RRH/RRU may beidentical to or different from the cell ID of an eNB. When the RRH/RRUand eNB use different cell IDs, both the RRH/RRU and eNB operate asindependent eNBs.

In a multi-node system according to the present disclosure, which willbe described below, one or more eNBs or eNB controllers connected toplural nodes can control the plural nodes such that signals aresimultaneously transmitted to or received from a UE through some or allnodes. While there is a difference between multi-node systems accordingto the nature of each node and implementation form of each node,multi-node systems are discriminated from single node systems (e.g. CAS,conventional MIMO systems, conventional relay systems, conventionalrepeater systems, etc.) since a plurality of nodes providescommunication services to a UE in a predetermined time-frequencyresource. Accordingly, embodiments of the present disclosure withrespect to a method of performing coordinated data transmission usingsome or all nodes can be applied to various types of multi-node systems.For example, a node refers to an antenna group spaced apart from anothernode by a predetermined distance or more, in general. However,embodiments of the present disclosure, which will be described below,can even be applied to a case in which a node refers to an arbitraryantenna group irrespective of node interval. In the case of an eNBincluding an X-pole (cross polarized) antenna, for example, theembodiments of the preset disclosure are applicable on the assumptionthat the eNB controls a node composed of an H-pole antenna and a V-poleantenna.

A communication scheme through which signals are transmitted/receivedvia plural transmit (Tx)/receive (Rx) nodes, signals aretransmitted/received via at least one node selected from plural Tx/Rxnodes, or a node transmitting a downlink signal is discriminated from anode transmitting an uplink signal is called multi-eNB MIMO or CoMP(Coordinated Multi-Point Tx/Rx). Coordinated transmission schemes fromamong CoMP communication schemes can be categorized into JP (JointProcessing) and scheduling coordination. The former may be divided intoJT (Joint Transmission)/JR (Joint Reception) and DPS (Dynamic PointSelection) and the latter may be divided into CS (CoordinatedScheduling) and CB (Coordinated Beamforming). DPS may be called DCS(Dynamic Cell Selection). When JP is performed, more variouscommunication environments can be generated, compared to other CoMPschemes. JT refers to a communication scheme by which plural nodestransmit the same stream to a UE and JR refers to a communication schemeby which plural nodes receive the same stream from the UE. The UE/eNBcombine signals received from the plural nodes to restore the stream. Inthe case of JT/JR, signal transmission reliability can be improvedaccording to transmit diversity since the same stream is transmittedfrom/to plural nodes. DPS refers to a communication scheme by which asignal is transmitted/received through a node selected from plural nodesaccording to a specific rule. In the case of DPS, signal transmissionreliability can be improved because a node having a good channel statebetween the node and a UE is selected as a communication node.

In the present disclosure, a cell refers to a specific geographical areain which one or more nodes provide communication services. Accordingly,communication with a specific cell may mean communication with an eNB ora node providing communication services to the specific cell. Adownlink/uplink signal of a specific cell refers to a downlink/uplinksignal from/to an eNB or a node providing communication services to thespecific cell. A cell providing uplink/downlink communication servicesto a UE is called a serving cell. Furthermore, channel status/quality ofa specific cell refers to channel status/quality of a channel or acommunication link generated between an eNB or a node providingcommunication services to the specific cell and a UE. In 3GPP LTE-Asystems, a UE can measure downlink channel state from a specific nodeusing one or more CSI-RSs (Channel State Information Reference Signals)transmitted through antenna port(s) of the specific node on a CSI-RSresource allocated to the specific node. In general, neighboring nodestransmit CSI-RS resources on orthogonal CSI-RS resources. When CSI-RSresources are orthogonal, this means that the CSI-RS resources havedifferent subframe configurations and/or CSI-RS sequences which specifysubframes to which CSI-RSs are allocated according to CSI-RS resourceconfigurations, subframe offsets and transmission periods, etc. whichspecify symbols and subcarriers carrying the CSI RSs.

In the present disclosure, PDCCH (Physical Downlink ControlChannel)/PCFICH (Physical Control Format Indicator Channel)/PHICH(Physical Hybrid automatic repeat request Indicator Channel)/PDSCH(Physical Downlink Shared Channel) refer to a set of time-frequencyresources or resource elements respectively carrying DCI (DownlinkControl Information)/CFI (Control Format Indicator)/downlink ACK/NACK(Acknowledgement/Negative ACK)/downlink data. In addition, PUCCH(Physical Uplink Control Channel)/PUSCH (Physical Uplink SharedChannel)/PRACH (Physical Random Access Channel) refer to sets oftime-frequency resources or resource elements respectively carrying UCI(Uplink Control Information)/uplink data/random access signals. In thepresent disclosure, a time-frequency resource or a resource element(RE), which is allocated to or belongs toPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH, is referred to as aPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE orPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH resource. In the followingdescription, transmission of PUCCH/PUSCH/PRACH by a UE is equivalent totransmission of uplink control information/uplink data/random accesssignal through or on PUCCH/PUSCH/PRACH. Furthermore, transmission ofPDCCH/PCFICH/PHICH/PDSCH by an eNB is equivalent to transmission ofdownlink data/control information through or onPDCCH/PCFICH/PHICH/PDSCH.

FIG. 1 illustrates an exemplary radio frame structure used in a wirelesscommunication system. FIG. 1(a) illustrates a frame structure forfrequency division duplex (FDD) used in 3GPP LTE/LTE-A and FIG. 1(b)illustrates a frame structure for time division duplex (TDD) used in3GPP LTE/LTE-A.

Referring to FIG. 1, a radio frame used in 3GPP LTE/LTE-A has a lengthof 10 ms (307200Ts) and includes 10 subframes in equal size. The 10subframes in the radio frame may be numbered. Here, Ts denotes samplingtime and is represented as Ts=1/(2048*15 kHz). Each subframe has alength of 1 ms and includes two slots. 20 slots in the radio frame canbe sequentially numbered from 0 to 19. Each slot has a length of 0.5 ms.A time for transmitting a subframe is defined as a transmission timeinterval (TTI). Time resources can be discriminated by a radio framenumber (or radio frame index), subframe number (or subframe index) and aslot number (or slot index).

The radio frame can be configured differently according to duplex mode.Downlink transmission is discriminated from uplink transmission byfrequency in FDD mode, and thus the radio frame includes only one of adownlink subframe and an uplink subframe in a specific frequency band.In TDD mode, downlink transmission is discriminated from uplinktransmission by time, and thus the radio frame includes both a downlinksubframe and an uplink subframe in a specific frequency band.

Table 1 shows DL-UL configurations of subframes in a radio frame in theTDD mode.

TABLE 1 Downlink- DL-UL to-Uplink config- Switch-point Subframe numberuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D DD D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6 5 ms D SU U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes threefields of DwPTS (Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS(Uplink Pilot TimeSlot). DwPTS is a period reserved for downlinktransmission and UpPTS is a period reserved for uplink transmission.Table 2 shows special subframe configuration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal Extended Normal Extended subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 ·T_(s) — — —

FIG. 2 illustrates an exemplary downlink/uplink slot structure in awireless communication system. Particularly, FIG. 2 illustrates aresource grid structure in 3GPP LTE/LTE-A. A resource grid is presentper antenna port.

Referring to FIG. 2, a slot includes a plurality of OFDM (OrthogonalFrequency Division Multiplexing) symbols in the time domain and aplurality of resource blocks (RBs) in the frequency domain. An OFDMsymbol may refer to a symbol period. A signal transmitted in each slotmay be represented by a resource grid composed of N_(RB) ^(DL/UL)*N_(sc)^(RB) subcarriers and N_(symb) ^(DL/UL) OFDM symbols. Here, N_(RB) ^(DL)denotes the number of RBs in a downlink slot and N_(RB) ^(UL) denotesthe number of RBs in an uplink slot. N_(RB) ^(DL) and N_(RB) ^(UL)respectively depend on a DL transmission bandwidth and a UL transmissionbandwidth. N_(symb) ^(DL) denotes the number of OFDM symbols in thedownlink slot and N_(symb) ^(UL) denotes the number of OFDM symbols inthe uplink slot. In addition, N_(sc) ^(RB) denotes the number ofsubcarriers constructing one RB.

An OFDM symbol may be called an SC-FDM (Single Carrier FrequencyDivision Multiplexing) symbol according to multiple access scheme. Thenumber of OFDM symbols included in a slot may depend on a channelbandwidth and the length of a cyclic prefix (CP). For example, a slotincludes 7 OFDM symbols in the case of normal CP and 6 OFDM symbols inthe case of extended CP. While FIG. 2 illustrates a subframe in which aslot includes 7 OFDM symbols for convenience, embodiments of the presentdisclosure can be equally applied to subframes having different numbersof OFDM symbols. Referring to FIG. 2, each OFDM symbol includes N_(RB)^(DL/UL)*N_(sc) ^(RB) subcarriers in the frequency domain. Subcarriertypes can be classified into a data subcarrier for data transmission, areference signal subcarrier for reference signal transmission, and nullsubcarriers for a guard band and a direct current (DC) component. Thenull subcarrier for a DC component is a subcarrier remaining unused andis mapped to a carrier frequency (f0) during OFDM signal generation orfrequency up-conversion. The carrier frequency is also called a centerfrequency.

An RB is defined by N_(symb) ^(DL/UL) (e.g. 7) consecutive OFDM symbolsin the time domain and N_(sc) ^(RB) (e.g. 12) consecutive subcarriers inthe frequency domain. For reference, a resource composed by an OFDMsymbol and a subcarrier is called a resource element (RE) or a tone.Accordingly, an RB is composed of N_(symb) ^(DL/UL)*N_(sc) ^(RB) REs.Each RE in a resource grid can be uniquely defined by an index pair(k, 1) in a slot. Here, k is an index in the range of 0 to N_(symb)^(DL/UL)*N_(sc) ^(RB)−1 in the frequency domain and 1 is an index in therange of 0 to N_(symb) ^(DL/UL)−1.

Two RBs that occupy N_(sc) ^(RB) consecutive subcarriers in a subframeand respectively disposed in two slots of the subframe are called aphysical resource block (PRB) pair. Two RBs constituting a PRB pair havethe same PRB number (or PRB index). A virtual resource block (VRB) is alogical resource allocation unit for resource allocation. The VRB hasthe same size as that of the PRB. The VRB may be divided into alocalized VRB and a distributed VRB depending on a mapping scheme of VRBinto PRB. The localized VRBs are mapped into the PRBs, whereby VRBnumber (VRB index) corresponds to PRB number. That is, n_(PRB)=n_(VRB)is obtained. Numbers are given to the localized VRBs from 0 to N_(VRB)^(DL)−1, and N_(VRB) ^(DL)=N_(RB) ^(DL) is obtained. Accordingly,according to the localized mapping scheme, the VRBs having the same VRBnumber are mapped into the PRBs having the same PRB number at the firstslot and the second slot. On the other hand, the distributed VRBs aremapped into the PRBs through interleaving. Accordingly, the VRBs havingthe same VRB number may be mapped into the PRBs having different PRBnumbers at the first slot and the second slot. Two PRBs, which arerespectively located at two slots of the subframe and have the same VRBnumber, will be referred to as a pair of VRBs.

FIG. 3 illustrates a downlink (DL) subframe structure used in 3GPPLTE/LTE-A.

Referring to FIG. 3, a DL subframe is divided into a control region anda data region. A maximum of three (four) OFDM symbols located in a frontportion of a first slot within a subframe correspond to the controlregion to which a control channel is allocated. A resource regionavailable for PDCCH transmission in the DL subframe is referred to as aPDCCH region hereinafter. The remaining OFDM symbols correspond to thedata region to which a physical downlink shared chancel (PDSCH) isallocated. A resource region available for PDSCH transmission in the DLsubframe is referred to as a PDSCH region hereinafter. Examples ofdownlink control channels used in 3GPP LTE include a physical controlformat indicator channel (PCFICH), a physical downlink control channel(PDCCH), a physical hybrid ARQ indicator channel (PHICH), etc. ThePCFICH is transmitted at a first OFDM symbol of a subframe and carriesinformation regarding the number of OFDM symbols used for transmissionof control channels within the subframe. The PHICH is a response ofuplink transmission and carries an HARQ acknowledgment (ACK)/negativeacknowledgment (NACK) signal.

Control information carried on the PDCCH is called downlink controlinformation (DCI). The DCI contains resource allocation information andcontrol information for a UE or a UE group. For example, the DCIincludes a transport format and resource allocation information of adownlink shared channel (DL-SCH), a transport format and resourceallocation information of an uplink shared channel (UL-SCH), paginginformation of a paging channel (PCH), system information on the DL-SCH,information about resource allocation of an upper layer control messagesuch as a random access response transmitted on the PDSCH, a transmitcontrol command set with respect to individual UEs in a UE group, atransmit power control command, information on activation of a voiceover IP (VoIP), downlink assignment index (DAI), etc. The transportformat and resource allocation information of the DL-SCH are also calledDL scheduling information or a DL grant and the transport format andresource allocation information of the UL-SCH are also called ULscheduling information or a UL grant. The size and purpose of DCIcarried on a PDCCH depend on DCI format and the size thereof may bevaried according to coding rate. Various formats, for example, formats 0and 4 for uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3 and 3Afor downlink, have been defined in 3GPP LTE. Control information such asa hopping flag, information on RB allocation, modulation coding scheme(MCS), redundancy version (RV), new data indicator (NDI), information ontransmit power control (TPC), cyclic shift demodulation reference signal(DMRS), UL index, channel quality information (CQI) request, DLassignment index, HARQ process number, transmitted precoding matrixindicator (TPMI), precoding matrix indicator (PMI), etc. is selected andcombined based on DCI format and transmitted to a UE as DCI.

In general, a DCI format for a UE depends on transmission mode (TM) setfor the UE. In other words, only a DCI format corresponding to aspecific TM can be used for a UE configured in the specific TM.

A PDCCH is transmitted on an aggregation of one or several consecutivecontrol channel elements (CCEs). The CCE is a logical allocation unitused to provide the PDCCH with a coding rate based on a state of a radiochannel. The CCE corresponds to a plurality of resource element groups(REGs). For example, a CCE corresponds to 9 REGs and an REG correspondsto 4 REs. 3GPP LTE defines a CCE set in which a PDCCH can be located foreach UE. A CCE set from which a UE can detect a PDCCH thereof is calleda PDCCH search space, simply, search space. An individual resourcethrough which the PDCCH can be transmitted within the search space iscalled a PDCCH candidate. A set of PDCCH candidates to be monitored bythe UE is defined as the search space. In 3GPP LTE/LTE-A, search spacesfor DCI formats may have different sizes and include a dedicated searchspace and a common search space. The dedicated search space is aUE-specific search space and is configured for each UE. The commonsearch space is configured for a plurality of UEs. Aggregation levelsdefining the search space is as follows.

TABLE 3 Number Search Space of PDCCH Type Aggregation Level L Size [inCCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 16 2 Common 416 4 8 16 2

A PDCCH candidate corresponds to 1, 2, 4 or 8 CCEs according to CCEaggregation level. An eNB transmits a PDCCH (DCI) on an arbitrary PDCCHcandidate with in a search space and a UE monitors the search space todetect the PDCCH (DCI). Here, monitoring refers to attempting to decodeeach PDCCH in the corresponding search space according to all monitoredDCI formats. The UE can detect the PDCCH thereof by monitoring pluralPDCCHs. Since the UE does not know the position in which the PDCCHthereof is transmitted, the UE attempts to decode all PDCCHs of thecorresponding DCI format for each subframe until a PDCCH having the IDthereof is detected. This process is called blind detection (or blinddecoding (BD)).

The eNB can transmit data for a UE or a UE group through the dataregion. Data transmitted through the data region may be called userdata. For transmission of the user data, a physical downlink sharedchannel (PDSCH) may be allocated to the data region. A paging channel(PCH) and downlink-shared channel (DL-SCH) are transmitted through thePDSCH. The UE can read data transmitted through the PDSCH by decodingcontrol information transmitted through a PDCCH. Informationrepresenting a UE or a UE group to which data on the PDSCH istransmitted, how the UE or UE group receives and decodes the PDSCH data,etc. is included in the PDCCH and transmitted. For example, if aspecific PDCCH is CRC (cyclic redundancy check)-masked having radionetwork temporary identify (RNTI) of “A” and information about datatransmitted using a radio resource (e.g., frequency position) of “B” andtransmission format information (e.g., transport block size, modulationscheme, coding information, etc.) of “C” is transmitted through aspecific DL subframe, the UE monitors PDCCHs using RNTI information anda UE having the RNTI of “A” detects a PDCCH and receives a PDSCHindicated by “B” and “C” using information about the PDCCH.

A reference signal (RS) to be compared with a data signal is necessaryfor the UE to demodulate a signal received from the eNB. A referencesignal refers to a predetermined signal having a specific waveform,which is transmitted from the eNB to the UE or from the UE to the eNBand known to both the eNB and UE. The reference signal is also called apilot. Reference signals are categorized into a cell-specific RS sharedby all UEs in a cell and a modulation RS (DM RS) dedicated for aspecific UE. A DM RS transmitted by the eNB for demodulation of downlinkdata for a specific UE is called a UE-specific RS. Both or one of DM RSand CRS may be transmitted on downlink. When only the DM RS istransmitted without CRS, an RS for channel measurement needs to beadditionally provided because the DM RS transmitted using the sameprecoder as used for data can be used for demodulation only. Forexample, in 3GPP LTE(-A), CSI-RS corresponding to an additional RS formeasurement is transmitted to the UE such that the UE can measurechannel state information. CSI-RS is transmitted in each transmissionperiod corresponding to a plurality of subframes based on the fact thatchannel state variation with time is not large, unlike CRS transmittedper subframe.

FIG. 4 illustrates an exemplary uplink subframe structure used in 3GPPLTE/LTE-A.

Referring to FIG. 4, a UL subframe can be divided into a control regionand a data region in the frequency domain. One or more PUCCHs (physicaluplink control channels) can be allocated to the control region to carryuplink control information (UCI). One or more PUSCHs (Physical uplinkshared channels) may be allocated to the data region of the UL subframeto carry user data.

In the UL subframe, subcarriers spaced apart from a DC subcarrier areused as the control region. In other words, subcarriers corresponding toboth ends of a UL transmission bandwidth are assigned to UCItransmission. The DC subcarrier is a component remaining unused forsignal transmission and is mapped to the carrier frequency f0 duringfrequency up-conversion. A PUCCH for a UE is allocated to an RB pairbelonging to resources operating at a carrier frequency and RBsbelonging to the RB pair occupy different subcarriers in two slots.Assignment of the PUCCH in this manner is represented as frequencyhopping of an RB pair allocated to the

PUCCH at a slot boundary. When frequency hopping is not applied, the RBpair occupies the same subcarrier.

The PUCCH can be used to transmit the following control information.

-   -   Scheduling Request (SR): This is information used to request a        UL-SCH resource and is transmitted using On-Off Keying (OOK)        scheme.    -   HARQ ACK/NACK: This is a response signal to a downlink data        packet on a PDSCH and indicates whether the downlink data packet        has been successfully received. A 1-bit ACK/NACK signal is        transmitted as a response to a single downlink codeword and a        2-bit ACK/NACK signal is transmitted as a response to two        downlink codewords. HARQ-ACK responses include positive ACK        (ACK), negative ACK (NACK), discontinuous transmission (DTX) and        NACK/DTX. Here, the term HARQ-ACK is used interchangeably with        the term HARQ ACK/NACK and ACK/NACK.    -   Channel State Indicator (CSI): This is feedback information        about a downlink channel. Feedback information regarding MIMO        includes a rank indicator (RI) and a precoding matrix indicator        (PMI).

The quantity of control information (UCI) that a UE can transmit througha subframe depends on the number of SC-FDMA symbols available forcontrol information transmission. The SC-FDMA symbols available forcontrol information transmission correspond to SC-FDMA symbols otherthan SC-FDMA symbols of the subframe, which are used for referencesignal transmission. In the case of a subframe in which a soundingreference signal (SRS) is configured, the last SC-FDMA symbol of thesubframe is excluded from the SC-FDMA symbols available for controlinformation transmission. A reference signal is used to detect coherenceof the PUCCH. The PUCCH supports various formats according toinformation transmitted thereon.

Table 4 shows the mapping relationship between PUCCH formats and UCI inLTE/LTE-A.

TABLE 4 Number of bits per PUCCH Modulation subframe, format schemeM_(bit) Usage Etc. 1 N/A N/A SR (Scheduling Request) 1a BPSK 1 ACK/NACKor One SR + ACK/NACK codeword 1b QPSK 2 ACK/NACK or Two SR + ACK/NACKcodeword 2 QPSK 20 CQI/PMI/RI Joint coding ACK/NACK (extended CP) 2aQPSK + BPSK 21 CQI/PMI/RI + Normal CP ACK/NACK only 2b QPSK + QPSK 22CQI/PMI/RI + Normal CP ACK/NACK only 3 QPSK 48 ACK/NACK or SR + ACK/NACKor CQI/PMI/RI + ACK/NACK

Referring to Table 4, PUCCH formats 1/1a/1b are used to transmitACK/NACK information, PUCCH format 2/2a/2b are used to carry CSI such asCQI/PMI/RI and PUCCH format 3 is used to transmit ACK/NACK information.

Reference Signal (RS)

When a packet is transmitted in a wireless communication system, signaldistortion may occur during transmission since the packet is transmittedthrough a radio channel. To correctly receive a distorted signal at areceiver, the distorted signal needs to be corrected using channelinformation. To detect channel information, a signal known to both atransmitter and the receiver is transmitted and channel information isdetected with a degree of distortion of the signal when the signal isreceived through a channel. This signal is called a pilot signal or areference signal.

When data is transmitted/received using multiple antennas, the receivercan receive a correct signal only when the receiver is aware of achannel state between each transmit antenna and each receive antenna.Accordingly, a reference signal needs to be provided per transmitantenna, more specifically, per antenna port.

Reference signals can be classified into an uplink reference signal anda downlink reference signal. In LTE, the uplink reference signalincludes:

i) a demodulation reference signal (DMRS) for channel estimation forcoherent demodulation of information transmitted through a PUSCH and aPUCCH; and

ii) a sounding reference signal (SRS) used for an eNB to measure uplinkchannel quality at a frequency of a different network.

The downlink reference signal includes:

i) a cell-specific reference signal (CRS) shared by all UEs in a cell;

ii) a UE-specific reference signal for a specific UE only;

iii) a DMRS transmitted for coherent demodulation when a PDSCH istransmitted;

iv) a channel state information reference signal (CSI-RS) for deliveringchannel state information (CSI) when a downlink DMRS is transmitted;

v) a multimedia broadcast single frequency network (MB SFN) referencesignal transmitted for coherent demodulation of a signal transmitted inMB SFN mode; and

vi) a positioning reference signal used to estimate geographic positioninformation of a UE.

Reference signals can be classified into a reference signal for channelinformation acquisition and a reference signal for data demodulation.The former needs to be transmitted in a wide band as it is used for a UEto acquire channel information on downlink transmission and received bya UE even if the UE does not receive downlink data in a specificsubframe. This reference signal is used even in a handover situation.The latter is transmitted along with a corresponding resource by an eNBwhen the eNB transmits a downlink signal and is used for a UE todemodulate data through channel measurement. This reference signal needsto be transmitted in a region in which data is transmitted.

In order to satisfy requirements for various application fields, it maybe considered to configure various transmission time intervals (TTIs)(or various TTI lengths) for all or a specific physical channel in thenext-generation system. More characteristically, a TTI during which aphysical channel such as a PDCCH/PDSCH/PUSCH/PUCCH is transmitted may beset to be less than 1 msec to reduce latency for communication betweenan eNB and a UE according to a scenario (such a PDCCH/PDSCH/PUSCH/PUCCHis referred to as an sPDCCH/sPDSCH/sPUSCH/sPUCCH). For a single UE ormultiple UEs, a plurality of physical channels may exist in a singlesubframe (e.g., 1 msec), and have different TTIs (or TTI lengths). Thefollowing embodiments will be described in the context of an LTE system,for the convenience of description. A TTI may be 1 msec (normal TTI),the length of a normal subframe used in the LTE system, and a short TTIis a TTI shorter than the normal TTI, spanning one or more OFDM orSC-FDMA symbols. While a short TTI (i.e., a TTI shorter than a legacyone subframe) is taken for the convenience of description, the keyfeatures of the present disclosure may be extended to a TTI longer thanone subframe or equal to or longer than 1 ms. Characteristically, thekey features of the present disclosure may also be extended to a shortTTI which is introduced to the next-generation system by increasing asubcarrier spacing. Although the present disclosure is described in thecontext of LTE, for convenience, the same thing is applicable to atechnology using a different waveform/frame structure such as new radioaccess technology (RAT). In general, the present disclosure is based onthe assumption of an sTTI (<1 msec), a longTTI (=1 msec), and alongerTTI (>1 msec).

Further, with a TTI maintained equal to 1 ms as in the legacy LTEsystem, a DL-to-UL timing (e.g., a time from DL data transmission to DLHARQ feedback transmission, or a time from UL grant transmission to ULdata transmission) may be reduced. This operation may be referred to asa shortened processing time operation.

When a UE operates in carrier aggregation (CA) or dual connectivity(DC), the UE may be configured with a plurality of serving cells, and anassumption or configuration for a shortened processing time and/or ashort TTI may be different for each cell. The serving cells may havedifferent TTI lengths, for example, when they have differentnumerologies such as subcarrier spacings. In the present disclosure, a“shortened processing time” refers to a DL data-to-DL HARQ-ACK timingand/or a UL grant-to-UL data timing, which is different from a legacyprocessing time.

CA with Shortened Processing Time

It may be regulated that a UE reports whether it supports a shortenedprocessing time operation by capability signaling. In this case, if theUE is configured with a shortened processing time, it may be regulatedthat the shortened processing time is applied to all carriers. It may beregulated that the UE reports whether the UE supports the shortenedprocessing time operation depending on whether the UE actually performsCA, or the UE reports whether the UE supports the shortened processingtime operation for each number of component carriers (CC) (or for eachrange consisting of a group of CC number) for which CA is actuallyperformed.

It may be regulated that the UE reports whether the UE supports theshortened processing time operation on a per band per band combinationbasis (on a per band per band-combination basis). According to thepresent proposal, the UE may report its capability of supporting theshortened processing time operation independently for each CC availablefor CA, which enables more flexible UE implementation. For example, a UEwith low processing power may report that the UE is capable ofsupporting the shortened processing time operation only for one of twoCCs available for CA, while a UE with high processing power may reportthat the UE is capable of supporting the shortened processing timeoperation for both of the CCs.

If the shortened processing time operation is supported in a specificband or band combination, a specific capability may also be reported.Specifically, it may be regulated that the UE reports a supportedprocessing time per band or per band combination. For example, thereport of the supported processing time may be a report of the shortestof supported processing times or a report of all supported shortenedprocessing times (e.g., when only n+2 and n+3 among n+1, n+2, and n+3are supported, n+2 and n+3 are reported as supported shortenedprocessing times).

It may be regulated that the UE reports a maximum number of CCs forwhich the shortened processing time operation may be supported in aspecific band, on a per band or per band combination basis. If thissignaling is introduced, the UE may report more elaborately whether theUE supports the shortened processing time operation for CCs ofintra-band contiguous CA. For example, even when intra-band contiguousCA is performed by using bandwidth class C in band x, it is possible tosupport the shortened processing time operation only for a part of aplurality of CCs included in band x.

Further, it may be regulated that the UE reports the capability ofsupporting the shortened processing time operation independently on a CCbasis, even for CCs of non-contiguous intra-band CA. Specifically, itmay be regulated that information indicating whether the shortenedprocessing time operation is supported on a band or band combinationbasis and/or information about a supported processing time and/or amaximum number of CCs for which the shortened processing time operationmay be supported is configured independently for each intra-band CC.

As the number of CCs aggregated for CA decreases, a CA-enabled UE mayhave more extra processing power, and support a shortened processingtime for more CCs with the extra processing power. Accordingly, it maybe regulated that for each number of CCs actually aggregated for CA, amaximum number of CCs for which the shortened processing time operationis supported is reported or pre-defined/pre-agreed.

Alternatively or additionally, it may be regulated if a CA-enabled UE isconfigured with a shortened processing time operation-relatedconfiguration, a CA operation is supported only for a predeterminednumber of or fewer CCs. It may be regulated that if a CA-enabled UE isconfigured with a shortened processing time operation-relatedconfiguration, one of the CA operation and the shortened processing timeoperation is disabled.

Alternatively or additionally, it may be regulated that differentmaximum numbers of CCs supporting the shortened processing timeoperation when CA is performed, and CCs supporting the shortenedprocessing time operation when CA is not performed are reportedindependently by a UE, or pre-defined/pre-agreed.

It may be regulated that when it is indicated to a UE whether theshortened processing time operation is supported on a band or CC basis,a maximum transport block (TB) size and/or a maximum timing advance (TA)and/or a maximum number of transmission layers and/or a maximum numberof transmission PRBs is limited on a band or CC basis. The restrictionsmay be pre-agreed or signaled. Particularly, the restrictions may bedifferent independently for each numerology (e.g., each TTI length orsubcarrier spacing). Alternatively or additionally, it may be regulatedthat if the shortened processing time operation is configured for theUE, the UE reports a supported maximum TB size and/or a supportedmaximum TA and/or a maximum number of transmission layers and/or amaximum number of transmission PRBs on a band or CC basis.

It may be regulated that if a specific CC is configured or activated fora UE, for the specific CC, the UE follows a processing time configuredfor a PCell without performing an additional (re)configuration processfor a processing time. Alternatively or additionally, it may beregulated that the UE follows the maximum (or minimum) of processingtimes configured for the UE, for a corresponding CC.

A plurality of processing times may be configured for a specific UE.Hereinbelow, a first processing time may be a timing which is notrelated to a shortened processing time configuration. In FDD, the firstprocessing time may be a timing or time taken for transmitting a DL HARQfeedback or UL data in subframe (SF) #n+4 or TTI #n+4 in response to DLdata or a UL grant transmitted in SF #n or TTI #n. In TDD, the firstprocessing time, which is basically at least 4ms, may become longer than4ms according to actual DL/UL subframes. A second processing time may bea new timing which is introduced according to a shortened processingtime configuration. For example, the second processing time may be is atiming or a time taken for transmitting a DL HARQ feedback or UL data inSF #n+3 or TTI #n+3 in response to DL data or a UL grant transmitted inSF #n or TTI #n. In TDD, the second processing time, which is basicallyat least 3ms, may become longer than 3ms according to actual DL/ULsubframes. For a single cell, the first processing time may be used fora fallback operation (e.g., for PDSCH/PUSCH scheduling by common searchspace (CS S) DCI and/or PDSCH scheduling by DCI format 1A, or for usinga general RNTI), whereas the second processing time may be used forapplying a shortened processing time (e.g., for PDSCH/PUSCH schedulingby user-specific search space (USS) DCI and/or PDSCH scheduling byTM-dependent DCI, or for using a third RNTI). A different configurationfor a shortened processing time operation may be used for each cell inCA or DC. Alternatively or additionally, different processing times maybe configured for a plurality of TTIs with different lengths.

If the timing of an HARQ-ACK feedback for a DL grant to which the firstprocessing time is applied overlaps wholly (or partially) with thetiming of an HARQ-ACK feedback for a DL grant to which the secondprocessing time is applied, it may be regulated that the number ofcodewords of a PDSCH scheduled by each of the DL grants is limited to 1.Characteristically, it may be regulated that the number of codewords ofa PDSCH scheduled by USS DCI or TM-dependent DCI is limited to 1 in theabove case. For example, if the transmission timing of an HARQ-ACKfeedback for a PDSCH scheduled in SF #n-4 by CSS DCI to which a legacyprocessing time is applied, and the transmission timing of an HARQ-ACKfeedback for a PDSCH scheduled in SF #n-3 by USS DCI to which ashortened processing time is applied are SF #n, it may be regulated thatthe number of codewords of the PDSCH scheduled by the USS DCI is limitedto 1 such that the total number of HARQ-ACK bits is 2. Alternatively oradditionally, it may be regulated that if there are two codewords of thePDSCH scheduled by the USS DCI or TM-dependent DCI, HARQ-ACK feedbacksare (spatially) bundled. The foregoing rules may be restrictivelyapplied only to a UE for which a specific PUCCH format (e.g., PUCCHformat 3/4/5) is not configured. If the transmission timings of HARQ-ACKfeedbacks for a predetermined number of or more codewords are wholly (orpartially) overlapped as in the above case, it may be regulated that thenumber of codewords of an SCell is first limited to 1 or HARQ-ACKfeedbacks for the codewords of the SCell are first (spatially) bundled.

In more general terms, it may be regulated in the above proposal that ifthe transmission timings of HARQ-ACK feedbacks for DL grants to which aplurality of different processing times are applied are wholly (orpartially) overlapped, the number of codewords of a PDSCH scheduled byeach of the DL grants is limited to 1. Characteristically, it may beregulated that the number of codewords is limited to 1 for a PDSCHscheduled by USS DCI or TM-dependent DCI. Alternatively or additionally,if there are two codewords of the PDSCH scheduled by the USS DCI orTM-dependent DCI, HARQ-ACK feedbacks are (spatially) bundled.

In the case where a UE performs an operation such as “reporting whetherit may support a shortened processing time operation for each number ofCCs actually aggregated for CA (or for each range including a group ofnumbers of CCs)”, “reporting a maximum number of CCs supporting theshortened processing time operation, for each number of CCs actuallyaggregated for CA”, or “independently reporting different maximumnumbers of CCs supporting the shortened processing time operation whenCA is performed and CCs supporting the shortened processing timeoperation when CA is not performed”, or in the case where the UEsimilarly reports its capability related to CA and the shortenedprocessing time operation, if more than carriers for which the UE iscapable of supporting the shortened processing time operation areconfigured/activated for the UE, it may be regulated that the UE followsa legacy processing time for all configured/activated carriers.Alternatively or additionally, if more than carriers for which the UE iscapable of supporting a shortened processing time areconfigured/activated for the UE in the above situation, it may beregulated that the UE follows a pre-defined or signaled specificprocessing time for all configured/activated carriers.

In cross-carrier scheduling (CCS), it may be regulated that theprocessing time of a scheduled cell is based on a processing timeconfigured for a scheduling cell at the time of scheduling.Alternatively or additionally, it may be regulated that the processingtime of the scheduled cell is based on a specific processing timesignaled by a higher-layer/physical-layer signal or implicitlyindicated.

In CA or DC, if different processing times are configured for ascheduling cell, a scheduled cell, and an HARQ transmitting cell (e.g.,PCell, PSCell, or a specific cell indicated/configured for transmittingan HARQ feedback), an actual DL assignment-to-DL data and/or ULgrant-to-UL data processing time may be determined as follows.Characteristically, the following rules may be applied for determining aprocessing time in the case of CCS.

-   -   Alt 1: An actual processing time may be determined according to        a processing time configured for a scheduled cell.        Characteristically, the rule may be applied for determining a UL        grant-to-UL data and/or DL assignment-to-DL data timing.    -   Alt 2: The actual processing time may be determined to be the        longer between a processing time configured for the scheduled        cell and a processing time configured for an HARQ transmitting        cell. For example, if processing times n+3 and n+4 are        configured respectively for the scheduled cell and the HARQ        transmitting cell, it may be regulated that a DL data-to-DL HARQ        transmission timing is n+4. That is, it may be regulated that        for operation with a shorter processing time (e.g., n+3), both        of the scheduled cell and the HARQ transmitting cell are        configured at least with the shorter processing time. Likewise,        the actual processing time may be determined to be the longer        between a processing time configured for the scheduling cell and        a processing time configured for the scheduled cell.    -   Alt 3: It may be regulated that CCS is allowed only when the        same processing time is configured for the scheduling cell and        the scheduled cell. Similarly, it may be regulated that the same        processing time configuration is always applied to the scheduled        cell and the HARQ transmitting cell. For example, if a shortened        processing time is not configured for the HARQ transmitting        cell, only a cell for which a shortened processing time is not        configured may be allowed as a scheduled cell.

Configuration of TTI Length/CA/Processing Time

If a UE is configured with an sTTI operation, the same or different DLsTTI lengths may be configured for cells. Characteristically, adifferent DL sTTI length may be configured for each cell group or eachPUCCH cell group. Alternatively or alternatively, a different DL sTTIlength may be configured for each TA group.

UL sTTI Length

If a UE is configured with an sTTI operation, the same or different ULsTTI lengths may be configured for cells. Characteristically, adifferent UL sTTI length may be configured for each cell group or PUCCHcell group. Alternatively or additionally, a different UL sTTI lengthmay be configured for each TA group. Alternatively or additionally, fora UE configured with an sTTI operation, only a single TA group may beconfigured for each cell group or PUCCH group.

Characteristically, the DL/UL TTI length configuration may beimplemented by a higher-layer or physical-layer signal.

More generally, if a UE is (additionally) configured with a numerologydifferent from a default numerology (hereinafter, referred to as a“different/additional numerology operation”), a different DL or ULnumerology may be configured for each cell group, PUCCH group, or TAgroup. The DL/UL numerology configuration may be implemented by ahigher-layer or physical-layer signal.

Processing Time Configuration

A processing time may be separately configured for each cell group,PUCCH group, or TA group. Characteristically, even for the same (DLand/or UL) sTTI length, a (different) processing time may be configuredseparately for each cell group, PUCCH group, or TA group. The processingtime may include a DL data-to-DL HARQ-ACK timing and/or UL grant-to-ULdata timing, and the two timings may be configured differently for eachcell group, PUCCH group, or TA group, (independently) for the same (DLand/or UL) sTTI length.

Configuration of Shorted Processing Time and sTTI

A UE may be configured with a shortened processing time operation and/oran sTTI operation. Characteristically, the following configurations areavailable.

The UE may independently derive and report the capability of a shortenedprocessing time operation and the capability of an sTTI operation (moregenerally, a different/additional numerology operation). That is, the UEmay separately report, to the network, the capability of the shortenedprocessing time operation supported by the UE in a situation in whichthe sTTI operation (or different/additional numerology operation) is notsupported, and/or the capability of the sTTI operation (ordifferent/additional numerology operation) supported by the UE in asituation in which the shortened processing time operation is notsupported. The capability signaling may be transmitted on a bandcombination basis. The UE may not expect that the shortened processingtime operation and the sTTI operation (or different/additionalnumerology operation) will be configured simultaneously.

Alternatively or additionally, the UE may report the joint capability ofthe shortened processing time operation and the sTTI operation (ordifferent/additional numerology operation). Alternatively oradditionally, the UE may report the joint capability of the sTTIoperation for different short TTI lengths (or different numerologies).The capability signaling may be transmitted on a band combination basis.For example, the UE may report by separate capability signaling whetherthe UE simultaneously supports a 7-symbol TTI operation and theshortened processing time operation, whether the UE simultaneouslysupports a 2-symbol TTI operation and the shortened processing timeoperation, and whether the UE simultaneously supports the 2-symbol TTIoperation and the 7-symbol TTI operation.

Alternatively or additionally, if the UE is configured with the sTTIoperation (or different/additional numerology operation), it may beregulated that CA is enabled only in a band combination in which thesTTI operation (or different/additional numerology operation) issupported.

Similarly, if the UE is configured with the shortened processing timeoperation, it may be regulated that CA is enabled only in a bandcombination in which the shortened processing time operation issupported.

Since examples of the above proposed methods may be included as one ofmethods of implementing the present disclosure, it is apparent that theexamples may be regarded as proposed methods. Further, the foregoingproposed methods may be implemented independently, or some of themethods may be implemented in combination (or merged). Further, it maybe regulated that information indicating whether the proposed methodsare applied (or information about the rules of the proposed methods) isindicated to a UE by a pre-defined signal (or a physical-layer orhigher-layer signal) by an eNB.

FIG. 5 illustrates an operation according to an embodiment of thepresent disclosure.

FIG. 5 depicts a method of supporting CA and a shortened processing timein a wireless communication system. The method may be performed by a UE.When the UE is configured with CA, the UE may report whether the UE iscapable of supporting a shortened processing time to an eNB (S510). Whenthe UE is configured with CCS, the UE may determine a processing timefor use in the UE (S520). The UE may perform a UL transmission operationaccording to the determined processing time (S530).

The report as to whether the shortened processing time is supported mayinclude information indicating whether the shortened processing time issupported for each number of carriers used for CA or for each group ofnumbers of carriers used for CA. Further, the report as to whether theshortened processing time is supported may be provided on a band basisor on a band combination basis. Further, the report as to whether theshortened processing time is supported may include information about asupported processing time in each band or band combination. Further, thereport as to whether the shortened processing time is supported mayinclude information about a maximum number of carriers for which theshortened processing time is supported in each band or band combination.

If more than the maximum number of carriers are configured or activatedfor the UE, a processing time for use in the UE may be determined to bea predetermined processing time.

In the case where two serving cells for CCS are configured for the UE,if the two serving cells have different processing times, the UE mayperform the UL transmission operation according to the longer betweenthe processing times of the two serving cells.

In the case where two serving cells for CCS are configured for the UE,the two serving cells may have the same processing time.

The UL transmission operation may include an operation of transmittingan HARQ feedback for DL data reception or a UL data transmissionoperation according to reception of a UL grant. Further, the UE may beconfigured to support two or more processing times. If the timings ofHARQ feedbacks for DL data receptions having different processing timesoverlap with each other, each DL data may be limited to one codeword.Alternatively or additionally, in the case where the timings of HARQfeedbacks for DL data receptions having different processing timesoverlap with each other, if DL data scheduled by specific DCI is twocodewords, HARQ feedbacks for the two codewords may be bundled.

If the cells aggregated for CA support a DL sTTI, a DL sTTI may beconfigured for each cell, each cell group, or each PUCCH cell group.Further, if the cells aggregated for CA support a UL sTTI, a UL sTTI maybe configured for each cell, each cell group, or each PUCCH cell group.

FIG. 6 is a block diagram of a transmitting device 10 and a receivingdevice 20 configured to implement exemplary embodiments of the presentdisclosure. Referring to FIG. 6, the transmitting device 10 and thereceiving device 20 respectively include transmitter/receiver 13 and 23for transmitting and receiving radio signals carrying information, data,signals, and/or messages, memories 12 and 22 for storing informationrelated to communication in a wireless communication system, andprocessors 11 and 21 connected operationally to the transmitter/receiver13 and 23 and the memories 12 and 22 and configured to control thememories 12 and 22 and/or the transmitter/receiver 13 and 23 so as toperform at least one of the above-described embodiments of the presentdisclosure.

The memories 12 and 22 may store programs for processing and control ofthe processors 11 and 21 and may temporarily storing input/outputinformation. The memories 12 and 22 may be used as buffers. Theprocessors 11 and 21 control the overall operation of various modules inthe transmitting device 10 or the receiving device 20. The processors 11and 21 may perform various control functions to implement the presentdisclosure. The processors 11 and 21 may be controllers,microcontrollers, microprocessors, or microcomputers. The processors 11and 21 may be implemented by hardware, firmware, software, or acombination thereof. In a hardware configuration, Application SpecificIntegrated Circuits (ASICs), Digital Signal Processors (DSPs), DigitalSignal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), orField Programmable Gate Arrays (FPGAs) may be included in the processors11 and 21. If the present disclosure is implemented using firmware orsoftware, firmware or software may be configured to include modules,procedures, functions, etc. performing the functions or operations ofthe present disclosure. Firmware or software configured to perform thepresent disclosure may be included in the processors 11 and 21 or storedin the memories 12 and 22 so as to be driven by the processors 11 and21.

The processor 11 of the transmitting device 10 is scheduled from theprocessor 11 or a scheduler connected to the processor 11 and codes andmodulates signals and/or data to be transmitted to the outside. Thecoded and modulated signals and/or data are transmitted to thetransmitter/receiver 13. For example, the processor 11 converts a datastream to be transmitted into K layers through demultiplexing, channelcoding, scrambling and modulation. The coded data stream is alsoreferred to as a codeword and is equivalent to a transport block whichis a data block provided by a MAC layer. One transport block (TB) iscoded into one codeword and each codeword is transmitted to thereceiving device in the form of one or more layers. For frequencyup-conversion, the transmitter/receiver 13 may include an oscillator.The transmitter/receiver 13 may include Nt (where Nt is a positiveinteger) transmit antennas.

A signal processing process of the receiving device 20 is the reverse ofthe signal processing process of the transmitting device 10. Under thecontrol of the processor 21, the transmitter/receiver 23 of thereceiving device 10 receives RF signals transmitted by the transmittingdevice 10. The transmitter/receiver 23 may include Nr receive antennasand frequency down-converts each signal received through receiveantennas into a baseband signal. The transmitter/receiver 23 may includean oscillator for frequency down-conversion. The processor 21 decodesand demodulates the radio signals received through the receive antennasand restores data that the transmitting device 10 wishes to transmit.

The transmitter/receiver 13 and 23 include one or more antennas. Anantenna performs a function of transmitting signals processed by thetransmitter/receiver 13 and 23 to the exterior or receiving radiosignals from the exterior to transfer the radio signals to thetransmitter/receiver 13 and 23. The antenna may also be called anantenna port. Each antenna may correspond to one physical antenna or maybe configured by a combination of more than one physical antennaelement. A signal transmitted through each antenna cannot be decomposedby the receiving device 20. A reference signal (RS) transmitted throughan antenna defines the corresponding antenna viewed from the receivingdevice 20 and enables the receiving device 20 to perform channelestimation for the antenna, irrespective of whether a channel is asingle RF channel from one physical antenna or a composite channel froma plurality of physical antenna elements including the antenna. That is,an antenna is defined such that a channel transmitting a symbol on theantenna may be derived from the channel transmitting another symbol onthe same antenna. A transmitter/receiver supporting a MIMO function oftransmitting and receiving data using a plurality of antennas may beconnected to two or more antennas.

In embodiments of the present disclosure, a UE serves as thetransmission device 10 on uplink and as the receiving device 20 ondownlink. In embodiments of the present disclosure, an eNB serves as thereceiving device 20 on uplink and as the transmission device 10 ondownlink.

The transmitting device and/or the receiving device may be configured asa combination of one or more embodiments of the present disclosure.

The detailed description of the exemplary embodiments of the presentdisclosure has been given to enable those skilled in the art toimplement and practice the disclosure. Although the disclosure has beendescribed with reference to the exemplary embodiments, those skilled inthe art will appreciate that various modifications and variations can bemade in the present disclosure without departing from the spirit orscope of the disclosure described in the appended claims. For example,those skilled in the art may use each construction described in theabove embodiments in combination with each other. Accordingly, thedisclosure should not be limited to the specific embodiments describedherein, but should be accorded the broadest scope consistent with theprinciples and novel features disclosed herein.

Industrial Applicability

The present disclosure may be used for a wireless communicationapparatus such as a user equipment (UE), a relay and an eNB.

1. A method for performing a communication by a user equipment (UE)supporting a shortened processing time in a wireless communicationsystem, the method comprising: reporting, to a base station (BS),capability information, wherein the capability information comprisesinformation related to whether the UE supports the shortened processingtime; and performing the communication with the BS according toconfigured shortened processing time.
 2. The method of claim 1, whereinthe report of the capability information is provided on a bandcombination basis.
 3. The method of claim 1, wherein the capabilityinformation further comprises information indicating a maximum number ofcarriers for which the shortened processing time is supported.
 4. Themethod of claim 3, wherein if more than the maximum number of carriersare configured or activated for the UE, a processing time for use in theUE is configured to be a predetermined processing time.
 5. The method ofclaim 1, wherein when two serving cells for cross-carrier scheduling areconfigured for the UE, if the two serving cells have differentprocessing times, the communication is performed according to a longerprocessing time of the processing times of the two serving cells.
 6. Themethod of claim 1, wherein when two serving cells for cross-carrierscheduling are configured for the UE, the two serving cells have thesame processing time.
 7. The method of claim 1, wherein thecommunication includes an operation of transmitting a hybrid automaticrepeat request (HARQ) feedback for downlink data reception or an uplinkdata transmission operation according to reception of an uplink grant.8. The method of claim 1, wherein the UE is configured to support two ormore processing times.
 9. The method according to claim 8, wherein ifthe timings of HARQ feedbacks for downlink data receptions havingdifferent processing times overlap with each other, each DL data islimited to one codeword.
 10. The method according to claim 8, whereinwhen the timings of HARQ feedbacks for downlink data receptions havingdifferent processing times overlap with each other, if downlink datascheduled by specific downlink control information is two codewords,HARQ feedbacks for the two codewords are bundled.
 11. The method ofclaim 1, wherein the capability information further comprisesinformation indicating whether the UE supports a short transmission timeinterval (TTI).
 12. The method of claim 11, wherein if cells aggregatedfor the carrier aggregation support at least one of a downlink short TTIor an uplink short TTI, a length of the at least one of the downlinkshort TTI or the uplink short TTI are configured for each cell, eachcell group, or each physical uplink control channel (PUCCH) cell group.13. The method of claim 12, wherein the length of the at least one ofthe downlink short TTI or the uplink short TTI is received through ahigher layer signal.
 14. A user equipment (UE) for supporting carrieraggregation and a shortened processing time in a wireless communicationsystem, the UE comprising: a receiver and a transmitter; and a processorconfigured to control the receiver and the transmitter, wherein theprocessor is further configured to: report, to a base station (BS),capability information, wherein the capability information comprisesinformation indicating whether the UE supports the shortened processingtime, and perform the communication with the BS according to aconfigured shortened processing time.
 15. The UE of claim 14, whereinthe capability information further comprises information indicatingwhether the UE supports a short transmission time interval (TTI).